Brown Mold

D&D 2024 hazard: Brown Mold. Source: Dungeon Master's Guide (2014). hazard type Hazard Brown mold feeds on warmth, drawing heat from anything around it. A patch of brown mold typically covers a 10-foot square, and the temperature within 30 feet of it is always frigid. When a creature moves to within 5 feet of the mold for the first time on a turn or starts its turn there, it must make a 12 Constitution saving throw, taking 22 (4d10) cold damage on a failed save, or half as much damage on a successful one. Brown mold is immune to fire, and any source of fire brought within 5 feet of a patch causes it to instantly expand outward in the direction of the fire, covering a 10-foot-square area (with the source of the fire at the center of that area). A patch of brown mold exposed to an effect that deals cold damage is instantly destroyed.